1. Field of the Invention
The present invention relates to a cable broadcasting system, and more particularly, to an emergency alert message data structure, an emergency alert message signaling method, and a cable broadcasting system.
2. Discussion of the Related Art
Generally, a digital cable set-top box is required for reception of digital cable broadcast. The digital cable set-top box is connected with a cable head-end, which is a kind of broadcasting station transmitting a digital cable program, to receive an audio/video (A/V) broadcasting program and data broadcast from the cable head-end. At this time, the A/V broadcasting program is received by In-Band signaling among cable frequency bands, and the data broadcast is received by Out-Of-Band (OOB) signaling among the frequency bands. In particular, the cable set-top box can perform two-way communication with the head-end by OOB signaling.
Broadcast protocols for transmission of channel and broadcasting program guide information may be, for example, Service Information (SI) protocol, and Program and System Information Protocol (PSIP). For the purpose of securing stability in the cable broadcast, SI is transmitted by OOB signaling, and PSIP information is transmitted by in-band signaling.
Digital cable broadcast receivers may be, for example, an open cable broadcast receiver adopted in America, a DVB-C broadcast receiver adopted in Europe, and an ISDB-C broadcast receiver adopted in Japan.
In the open cable broadcast receiver, a Point Of Deployment (POD) module with a conditional access (CA) system is separated from the body of a digital cable set-top box in order to prevent copying of high value-added broadcast content and to allow a conditional access thereto. It is thus possible to readily replace a security system with another one and retail the broadcast receiver. Therefore, the digital cable broadcast receiver has the advantage of being capable of being supplied at a low price.
The POD module is inserted in a slot of the digital cable set-top box. In this regard, the POD module is often called a cable card. The term ‘POD module’ and the term ‘cable card’ will hereinafter be used interchangeably.
Meanwhile, a cable set-top box-embedded cable broadcast receiver (for example, a cable ready digital TV) has been proposed to enable a retail sale that the open cable system pursues.
This cable broadcast receiver contains a cable set-top box so that the user can receive and view all terrestrial analog broadcast, terrestrial digital broadcast, cable analog broadcast and cable digital broadcast without using a separate cable set-top box.
A basic convention is defined in the cable broadcast receiver to properly receive and process an emergency alert message if a transmitter transmits the emergency alert message to warn of a state of emergency.
That is, if a transmitter transmits an emergency alert message at a specific terrestrial frequency or cable frequency, the cable broadcast receiver receives the transmitted emergency alert message. Then, the cable broadcast receiver outputs information regarding a channel change to a specific terrestrial or cable emergency broadcast channel and an emergency alert to the viewer in order to effectively provide the emergency alert information to the viewer. At this time, the emergency alert information can be outputted in the form of text and/or audio. For example, when the emergency alert information is in the form of text, it may be displayed for a predetermined time while being scrolled from the upper right to upper left of the screen.
The scroll rate of emergency alert contents in text form contained in the emergency alert message is determined by the cable broadcast receiver. That is, the cable broadcast receiver scrolls the emergency alert contents at a predetermined fixed scroll rate or a scroll rate calculated with reference to the received emergency alert message.
As described above, conventionally, the scroll rate of the emergency alert contents in text form contained in the emergency alert message is determined by the cable broadcast receiver.
As a result, even though scroll data has the same size and contents, the scroll rate thereof may be different according to receiver manufacturers (for example, LG, SAMSUNG, etc.) and the types of receivers from the same manufacturer because scroll rate is not standardized.
For example, a receiver of a manufacturer A may scroll the emergency alert contents so fast that the viewer may not accurately recognize a state of emergency, and, on the contrary, a receiver of a manufacturer B may scroll the emergency alert contents so slowly that the viewer may feel irritated.
On the other hand, at the time that the emergency alert is released, the cable broadcast receiver must return to the original state prior to the emergency alert. For example, the cable broadcast receiver must restore the current channel from the emergency broadcast channel to the original channel, viewed by the viewer prior to the emergency broadcast channel, if the original channel was compulsorily changed to the emergency broadcast channel.
However, provided that the emergency alert is released under the condition that data to be scrolled remains, the emergency alert contents will be continuously scrolled on the screen in spite of the fact that the emergency alert has been released.
In this case, the viewer has no choice but to continuously view unnecessary information being scrolled under the condition that he/she does not know how long the unnecessary information will be scrolled. As a result, the viewer may feel irritated and inconvenienced.